Light reference system for railroad track surveying

ABSTRACT

This invention relates to reference systems of the type used for surveying railroad track in which a light beam transmitter, a beam receiver spaced therefrom and a railroad condition sensor having a single edged shadow board is located therebetween. The invention contemplates positioning at least two photo-cells in the receiver physically closely spaced apart in the direction of shadow board motion. The outputs from the photo-electric cells are electrically connected in a differential configuration so that a command signal is generated to stop shadow board movement into the transmitted beam when the shadow board reaches a datum position at which point the distribution of the transmitted light on the photo-cells will have achieved a predetermined difference. In one aspect of the invention a deadband producing photo-cell is provided in the receiver and located physically closely spaced apart from the other two photo-cells in the direction of the shadow board motion and inwardly of the edge thereof when it is in datum position. The deadband producing photo-cell is electrically connected to generate a command signal to commence shadow board movement into the beam when the deadband producing photo-electric cell is exposed by a predetermined amount to the transmitted beam.

United States Patent Bencsics et al.

[54] LIGHT REFERENCE SYSTEM FOR RAILROAD TRACK SURVEYING [72] Inventors: Odon Steven Bencsics, 4917 Coronation Ave., Montreal, Quebec, Canada; Helmut Rolf Erich Von Beckmann, 189 Castle Road, Columbia, SC. 29210 [22] Filed: Sept. 5, 1969 [21] Appl.No.: 855,591

3,381,626 5/1968 Fagan et al. 33/60 X 3,444,384 5/1969 Horeczky... 250/204 X 3,521,066 7/1970 .loy et al..... ..33/60 X 3,218,623 11/1965 Buntenbach ..340/258 C UX 1 1 July 4, 1972 Primary Examiner.lohn W. Caldwell Assistant Examiner-Michael Slobasky Attorney-Smart and Biggar [57] ABSTRACT This invention relates to reference systems of the type used for surveying railroad track in which a light beam transmitter, a beam receiver spaced therefrom and a railroad condition sensor having a single edged shadow board is located therebetween. The invention contemplates positioning at least two photo-cells in the receiver physically closely spaced apart in the direction of shadow board motion. The outputs from the photo-electric cells are electrically connected in a differential configuration so that a command signal is generated to stop shadow board movement into the transmitted beam when the shadow board reaches a datum position at which point the distribution of the transmitted light on the photo-cells will have achieved a predetermined difference. In one aspect of the invention a deadband producing photo-cell is provided in the receiver and located physically closely spaced apart from the other two photo-cells in the direction of the shadow board motion and inwardly of the edge thereof when it is in datum position. The deadband producing photo-cell is electrically connected to generate a command signal to commence shadow board movement into the beam when the deadband producing FOREIGN PATENTS QR APPLICATIONS photo-electric cell is exposed by a predetermined amount to the transmitted beam. 737,154 6/1966 Canada ..33/60 5 Claims, 2 Drawing Figures 12 TRACK 3 j, SBHOAADRO W 2| 22 23 2o 1 BEAM l l 4 1Q AMPL'F'ER WEIGHING (START l5 NETWORK CORRECTION PROJECTOR AMPLIHER POTENTIOMETER l8 I20 ls/ SUMMING TRIGGER cmcun WElGHING (STOP AMPLIFlER NETWORK ALARM CIRCUIT 25 PATENTEDJUL 4 I972 HELMUTH R. E. von BECKMANN SMART a BIGGAR ATTORNEYS LIGHT REFERENCE SYSTEM FOR RAILROAD TRACK SURVEYING BACKGROUND OF INVENTION This invention relates to reference systems of the type which use a beam transmitter, usually a light beam projector which transmits a reference beam towards a receiver and in which a single edged shadow board is mounted on a road condition sensor between the transmitter and the receiver.

In the past systems of this nature, particularly when used for railroad surfacing work, have used a single edged shadow board positioned closer to the receiver than to the transmitter. In the conditions where fog, or dust-laden air, was encountered during a surveying operation, a good deal of scatter of the transmitted reference light beam took place and consequently the cut-oi? point of the shadow board in the transmitted beam was afiected. Thus, surveying or track correcting operations were hampered by the receiver being able to receive quantities of energy from the scattered light beyond the shadow board single edge and whereas in clear air conditions a positive repeatable cut-off datum point for the shadow board was readily established, in fog and like conditions the datum cut-off point of the shadow board was not readily ascertainable or repeatable.

SUMMARY OF INVENTION It is an object of the present invention to provide a receiver for use with a single edged shadow board which is less affected by light scatter under adverse surveying conditions than receivers heretofore used.

Accordingly, the present invention provides in a reference system of the type described, the improvement wherein the receiver includes at least two light sensitive transducers physically closely spaced apart in the direction of shadow board motion; and means for electrically connecting the outputs from the transducers in a differential configuration whereby to roduce a command signal to stop shadow board movement when the shadow board is positioned at a datum position in the transmitted beam so as to distribute the transmitted light on the transducers with a predetermined difference.

According to a feature of the present invention a deadband producing transducer is provided for the system and is physically closely spaced apart from the first mentioned transducers in the direction of the shadow board motion and inwardly of the shadow board edge when it is in datum position; and means electrically connecting the output from the deadband transducer to the output from the transducer close to the shadow board edge, when it is in datum position, to provide a command signal to commence shadow board movement into the beam when said deadband producing transducer is exposed by a predetermined amount to the transmitted beam.

BRIEF DESCRIPTION OF THE DRAWINGS The following is a description by way of example, of two embodiments of the invention, reference being had to the accompanying drawings in which:

FIG. 1 which is a schematic representation of the device; and

FIG. 2 is a diagrammatic representation of the device according to FIG. 1, further modified by the inclusion of a deadband transducer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings there is schematically shown a surveying system of the type generally in use on railroads where a projector 10, of infra-red light, is mounted on a satellite car which precedes a track surveying or correcting car along the track. A receiver 12 is mounted on the surveying or correcting car and a track condition sensor having a shadow board 13 is mounted between the projector and receiver. The arrangement may be for a track surveying or alignment operation, or for a track horizontal condition surveying or alignment operation. However, as shown in FIGS. 1 and 2, the system of the invention is utilized for a track aligning operation.

Referring now particularly to FIG. I. The receiver 12 has two transducers or photo cells 14 and 15 which convert the beam energy received from the projector 10 into a useful electrical signal. The photo cells 14 and 15 are mounted in the receiver 12 physically closely spaced apart in the direction of shadow board motion, in this instance, transversely of the track. Two amplifier stages 16 and 17 bring the signal from the photo cells 14 and 15 up to an output level, if necessary. Further, the amplification stages can include tuning," if the transmitted beam is modulated, and detection to convert the alternating signal to direct current. The stages 16 and 17 may also include adjustable gain controls.

A summing and weighing network 18 provides an operating signal to a trigger network 19 when the signals from the photoelectric cells 16 and 17 are in a predetermined ratio to one another, say 2-1 for the photo cell 15 relative to the photo cell 14. The trigger circuit 19 is arranged to react to the sum from the station 18 and provides the type of control output required in the application of the receiver. In this embodiment the trigger network controls a relay which may operate to stop the movement of the shadow board into the projected beam when it reaches the datum position shown in FIG. 1, at which datum position the shadow board shades the photo-electric cell 14 and provides it with only half of the energy which is received by the photo-electric cell 15 because the photo-cell 15 is still outside (or more remote from) the shadow board edge. In a surveying mode the relay will operate to stop the outward drive of the shadow board itself while in an aligning mode the relay will operate a track-moving jack to throw the track, with the shadow board thereon, towards the transmitted beam.

In some applications of the system according to the invention, particularly alignment operations of railway track, it is desirable that corrections not be made in alignment unless the errors in the track are of a predetermined sufficient magnitude. This magnitude of error is referred to as a deadband.

The nature of the system as described, with reference to FIG. 1, because the necessary proximity of the photo cells 14 and 15, is such that the slightest motion of the shadow board away from the beam changes the ratio sufiiciently to fire the trigger circuit and cause correction. The deadband in such a circuit is probably less than one sixty-fourths of an inch.

In the embodiment in FIG. 2, in addition to the photo-cells 14 and 15 a deadband photo cell 20 is provided in the receiver 12 physically closely spaced apart from the photo cells 14 and 15 in the direction of shadow board motion and inwardly of its edge when it is in datum position. The cell 20 has its own amplification stage 21, similar to amplifiers l6 and 17, the output of which passes to a second summing and weighing network 22 which also receives the output from the amplifier 16.

The shadow board 13 will have to be retracted away from the transmitted beam sufficiently to establish a predetermined ratio of signal from the photo-electric cell 14 and the photoelectric cell 20 before the summing and weighing circuit 22 will fire the trigger circuit 23 and thereby initiate corrective action by moving the shadow board back into the beam. This ensures that a detected error is of sufficient magnitude to warrant correction before corrective action is taken.

The network 22 may be adjustable, for example, by the setting of a potentiometer to produce a controllable deadband. It is to be understood that alternatively, the photo cells 14 and 15, or the photo cells l4, l5 and 20, may be physically mounted so as to be adjustable in their spacing in the direction of the shadow board motion, if required to vary the ratios involved.

Of course it is to be understood that if the track error is such as to cause the shadow board to observe both the photo cells 14 and 15 a signal will be generated, in usual fashion to move the track out of the transmitted beam.

If desired, a second receiver 12a may be mounted outwardly of the receiver 12 and be connected to an alarm circuit 25 such that if an operator inadvertently stands into the path of the transmitted beam, such that the receiver 12 will be obscured from the transmitter, an alarm will be sounded.

What we claim as our invention is:

1. In a reference system comprising a light beam projector, a beam receiver spaced therefrom, a road condition sensor including a single edged shadow board therebetween, the improvement wherein the receiver includes at least two photoelectric cells physically closely spaced apart in the direction of shadow board motion; and means for electrically connecting the outputs from the cells whereby to produce a command signal to stop shadow board movement when the shadow board is positioned at a datum position in the transmitted beam so as to distribute the transmitted light on the cells with a predetermined difference and in which a deadband producing transducer is provided physically closely spaced apart from the said two cells in the direction of the shadow board motion and inwardly of the shadow board edge when it is in datum position; means electrically connecting the output from the deadband producing transducer to the output from the cell close to the shadow board edge, when it is in datum position, to provide a command signal to commence shadow board movement into the beam when said deadband producing transducer is exposed by a predetermined amount to the transmitted beam, which means electrically connecting the output from the deadband producing transducer to the output from the cell close to the shadow board edge, include amplifying means for that cell and for said transducer and a summing and weighing network electrically connected to receive the output signals from each of the amplifying means and adapted to produce an operating signal when the output signals from the amplifying means are in a predetermined ratio to one another; and a trigger circuit activated by said operating signal and providing the command signal to commence shadow board movement into the beam.

2. A system as claimed in claim 1 wherein said summing and weighing network is adjustable.

3. A system as claimed in claim 1 wherein said summing and weighing network is adjustable by potentiometer setting whereby to produce a controllable deadband 4. A system as claimed in claim 3 wherein the output from the photo-electric cell remote from the shadow board edge is amplified in an amplifying means and wherein a second summing weighing network is electrically connected to receive the output signals from the amplifying means for said outermost photo cell and from the amplifier for said inner photo cell which second summing and weighing network produces an operating signal when the output signals from the two amplifying means connected thereto are in a predetermined ratio to one another; and a second trigger circuit activated by said operating signal from said second summing and weighing circuit and providing a control signal to retract the shadow board out of the transmitted beam.

5. A device as claimed in claim 4 in which a second receiver is provided outwardly of the first receiver and is electrically connected to an alarm system operable if the transmitted beam is inadvertantly interrupted. 

1. In a reference system comprising a light beam projector, a beam receiver spaced therefrom, a road condition sensor including a single edged shadow board therebetween, the improvement wherein the receiver includes at least two photo-electric cells physically closely spaced apart in the direction of shadow board motion; and means for electrically connecting the outputs from the cells whereby to produce a command signal to stop shadow board movement when the shadow board is positioned at a datum position in the transmitted beam so as to distribute the transmitted light on the cells with a predetermined difference and in which a deadband producing transducer is provided physically closely spaced apart from the said two cells in the direction of the shadow board motion and inwardly of the shadow board edge when it is in datum position; means electrically connecting the output from the deadband producing transducer to the output from the cell close to the shadow board edge, when it is in datum position, to provide a command signal to commence shadow board movement into the beam when said deadband producing transducer is exposed by a predetermined amount to the transmitted beam, which means electrically connecting the output from the deadband producing transducer to the output from the cell close to the shadow board edge, include amplifying means for that cell and for said transducer and a summing and weighing network electrically connected to receive the output signals from each of the amplifying means and adapted to produce an operating signal when the output signals from the amplifying means are in a predetermined ratio to one another; and a trigger circuit activated by said operating signal and providing the command signal to commence shadow Board movement into the beam.
 2. A system as claimed in claim 1 wherein said summing and weighing network is adjustable.
 3. A system as claimed in claim 1 wherein said summing and weighing network is adjustable by potentiometer setting whereby to produce a controllable deadband.
 4. A system as claimed in claim 3 wherein the output from the photo-electric cell remote from the shadow board edge is amplified in an amplifying means and wherein a second summing weighing network is electrically connected to receive the output signals from the amplifying means for said outermost photo cell and from the amplifier for said inner photo cell which second summing and weighing network produces an operating signal when the output signals from the two amplifying means connected thereto are in a predetermined ratio to one another; and a second trigger circuit activated by said operating signal from said second summing and weighing circuit and providing a control signal to retract the shadow board out of the transmitted beam.
 5. A device as claimed in claim 4 in which a second receiver is provided outwardly of the first receiver and is electrically connected to an alarm system operable if the transmitted beam is inadvertantly interrupted. 